The present invention relates to timber saws and more particularly to mobile saws for sawing timber into suitable lengths for transportation and use as telegraph poles, pulp wood, and the like.
The desirability of mobile radial arm timber saws is well known. Known saws have utilized trailer mounted radial arm assemblies in which the radial saw is boom mounted and moved horizontally in the cutting operation across timber placed in the bed of the trailer.
Control of the movement of the saw both in the cutting and retracting motions has been a problem with known saws. A hydraulic piston is customarily used to position the saw. This piston must necessarily be attached both to the trailer base as the stationary side of a parallelogram as well as to the saw boom through an appropriate linkage so that the saw boom may form the opposite side of the parallelogram. The force of the hydraulic piston acting on the saw boom moves the parallelogram and then the saw across the trailer bed in the cutting operation.
In known timber saws, there is generally a position adjacent the fully retracted saw position in which control of the saw is not positively maintained. Spring members, generally coil or flat springs, are used to insure that the saw, once in this little or no power position, may continue to move through such position to either the fully retracted or fully extended positions. Control problems near this point are exacerbated by any wear of the linkage assembly.
In addition to the lack of control over the position of the saw adjacent the fully withdrawn position, the known saw assemblies, once the spring bias is overcome, typically cause the saw to accelerate rapidly across the trailer bed. This initial acceleration in the feed of the saw into the timber may result in "bucking" or stalling of the saw. These and other problems are obviated by the present invention which includes a linkage assembly which insures positive control of the position of the saw boom vis-a-vis trailer bed at all times. This positive control of the saw includes control of the speed of saw movement across the trailer bed.
These and many other advantages will be readily apparent from the claims and from the following detailed description when viewed in connection with the appended drawings.